1. Explain how steps in a procedure remove impurities
In: Chemistry
Which of the following substances has the lowest boiling point? C12H16 CH2Br2 Br2 ICl
How much energy in kJ will it take to melt 5.0 g of frozen Ar at -190o C?
T/F if methane was at -50o C it cannot be made to liquify at any pressure.
If H2O at -1.0o C and 1.0 atm has enough pressure applied to it, what phase change, if any, can occur?
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solid to liquid |
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liquid to solid |
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stays solid |
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stays liquid What is the concentration in percent by mass when a solution is prepared by dissolving 8.00 g of NaCl into 70.0 g of water? What kind of solute gets more soluble as the temperature of the solvent decreases? The normal vapor pressure of water at 30o C is 31.82 mmHg. When 25.0 g of glucose (C6H12O6) are dissolved in 25.0 g of water at 30o C, what is the solution's vapor pressure? What is the freezing point of a solution made up of 150.0 g of benzene (normal fp=5.5o C, Kf=5.12 oC/m) with 0.200 moles of naphthalene dissolved in them? |
In: Chemistry
Consider the following reaction between oxides of nitrogen: NO2(g)+N2O(g)?3NO(g)
1.
Calculate ?G? at 800 K, assuming that ?H? and ?S? do not change with temperature.
Express your answer using two significant figures.
2.Calculate ?G? at 1000 K.
In: Chemistry
If a solution containing 45 g of mercury(II) nitrate is allowed to react completely with a solution containing 14.334 g of sodium sulfate. a)How many grams of solid precipitate will be formed? b)How many grams of the reactant in excess will remain after the reaction?
In: Chemistry
Consider a 0.5 M solution of trimethylammonium chloride. The ion trimethylammonium is the conjugate acid of the the weak base trimethylamine.The pKb of trimethylamine is 4.2
A) Calculate [H+]
B) calculate the concentration of trimethylammonium ions
C) calculate the concentration of trimethylamine in equilibrium
D) calculate [OH-]
E) Calculate [Cl-]
F) Calculate the pH
In: Chemistry
A flask contains a gaseous mixture of 3.01mol of hydrogen and 5.84mol of oxygen gases. When these gases react, steam is produced.
a) Balance the equation for this reaction. H2(g) + O2(g) H2O(g)
b) What is the limiting reagent?
c) How many grams of steam are produced?
d) How many moles of limiting reagent remain unreacted? e) How many
moles of excess reagent remain unreacted?
In: Chemistry
A flask with a sample of gas at room temperature and pressure weighs 97.4842 g. The same flask with air (density = 1.17 g/L) weighs 96.8848 g. The same flask filled with water (d = 0.998 g/mL) weighs 345.86 g. The pressure in the room is 0.989 atm and the temperature is 22.2 °C.
1. Calculate the volume of the flask.
2. Calculate the mass of the air that the flask can hold.
3. Calculate the mass of the empty (no air) flask.
4. Calculate the mass of the gas in the flask.
5. Use the Ideal gas law to calculate the moles of gas in the flask.
6. Calculate the molar mass of the gas in the flask.
In: Chemistry
4. Calculate the pH of the following salt solutions (5 pts each). a. 0.237 M sodium cyanide, NaCN (aq) (HCN ka = 4.0 x 10-10) b. 0.166 M ammonium iodide, NH4I (aq) (NH4+ ka = 5.6 x 10-10)
In: Chemistry
Molecular Orbital Theory
1.1 Which model, the Lewis electron dot structure or the MO energy level diagram, better describes the bonding in O2? Remember that liquid O2 is attracted into the magnetic field of a large magnet.
True or False.
_____ MO theory allows us to avoid the use of resonance.
_____ Resonance is a concept which arises from the limitations of Lewis electron dot structures
1.2 As we go from Li2 to Li3 to Li4 to Lin, the number of molecular orbitals formed from the 2s atomic orbitals goes from 2 to __ to __ to __ respectively, and the spacing between energy levels _________.
1.3 In the case of a metal, the lowest unoccupied MO is only infinitesimally higher in energy than the highest occupied MO, so it takes very little energy to cause electrons to move in a metal wire. In the case of a semiconductor, there is a _____ band gap between the full valence band and the empty conduction band. In the case of an insulator, there is a _____ band gap between the full valence band and the empty conduction band.
In: Chemistry
Explain these facts: (a) Copper and iron have several oxidation states, whereas zinc exists in only one.
(b) Copper and iron form colored ions, whereas zinc does not.
(c)Hydrated Mn2+ ions are practically colorless even though they possess five 3d electrons.
In: Chemistry
find the ratio effusion rates of hydrogen gas and krytpon gas.
In: Chemistry
Using only the elements Ca, Cl, Si, give formulas for the following: (a) an ionic compound. (b) a molecular compound with polar covalent bonds that obeys the octect rule and has no formal charge. For part b I drew the lewis structure Cl(double bond)-Ca-(double bond)Cl with two lone pair on each chloride, is that correct? Please explain. Thank you.
In: Chemistry
what is the difference between absorption and emission? transmission and reflection?
when plotting a graph of A vs B, what does it mean if one says that A is directly proportional to B? what would the graph look like?
what are the four steps of the scientific method?
In: Chemistry
You used 50.0mL of hydrochloric acid with 0.500g of magnesium. If the temperature changed from 20.0oC to 24.0oC, what was the heat of reaction (ΔH) for your experiment? Report your answer in kJ without writing the units.
In: Chemistry